. >>> from new york city, this is "nightline" with bill weir. >> if the last 600 years have taught us anything it's that popes don't quit. there is no holy father rest home. it is a job for life or at least it was until this morning when over a billion catholics did a double take over the news that benedict xvi had given his two weeks' notice in latin. why now and what does it mean for the church? who could possibly replace him. here's terry moran. >> reporter: an ordinary rainy monday in the vatican except for that lightning bolt striking the vatican. the pope gathered the cardinal together. his bombshell came at the end. [ speaking foreign language ] he spoke in latin, the ancient language of the church. i have come to the certainty, he says that my strengths due to an advanced age are no longer suited to an adequate exercise of the papacy. >> i'm shocked. >> reporter: around the world, the reaction was the same. >> today's decision by benedict xvi to resign from the papacy came as a huge surprise to me and to everyone in rome and in the vatican. >> reporter: it hadn't happened for